Since the forecast in the next few weeks is still good for my target temp of somewhere between 11-13 degrees C, I did a lager brew yesterday.
I also thought that this might be a good chance to show you my converted Sanke Keg used as a fermentation chamber for a larger batch. These Stainless Kegs are often used by folks for brewing systems and make nice kettles. If you take a bit of care when you cut off the top then you can also use them as a fermenter for large batches of 10-13 Gallons (50 Liters).
The top of this Sanke has been carefully cut in a perfect (well - within limits) circle of 11". You really don't want to go larger than 12" and if you make it smaller then the fermenter function is easier but the kettle is a little harder. My cutting was done with a dremel and a couple of fiberglass cuttoff wheels (dremel calls these "heavy duty"). Sure you could do the cut with an angle grinder but you lose significant precision and spend a lot of extra time cleaning up the edge. Cutting with a dremel will take a total of 15 minutes (it seems like longer when you are actually doing it). You will need to make multiple passes and you will burn through 2-3 wheels. It's easy to follow circular line that you can mark out with a sharpie and piece of string as a makeshift compass.
|Converted Sanke Fermenter|
For the fermenter cover, I use a 1/4" lucite (available at your local big box hardware store). I would not recommend any thinner lucite stock which would not be rigid enough (you could back it with plywood but then would lose your transparent "window"). The lucite is easily cut with a jigsaw (low speed - take your time and avoid melting . The warning goes double for drilling out the bung hole - go too fast with too much pressure and the sheet could crack). The edge of the lucite can be smoothed with a file.
The cover needs a gasket to make an airtight seal. The neoprene gasket I use is just taken from the lid gasket of a typical food grade 6 gallon bucket (the kind that some folks use a fermenter). If you have no access to these very common buckets/lids then I believe that the empty paint buckets that Home Depot sells - their lids have a usable gasket. So you can see, the size of the hole in the Sanke is just a bit smaller than the gasket that is used.
Now you need to hold down the lid. Luckily these kegs have handy handles that we can use for the purpose. By passing some kind of rigid rod via the handles we can set a bolt to push down on the lid.
|Lid Holder Configuration|
In my case I use square aluminum stock but if you have stainless steel that would be pretty cool.
My first cover lasted a few years and then developed cracks at the push-down point. This second cover uses an intervening plastic disc (just a very rigid bottom from some forgotten container that my wife was throwing out of the kitchen - a disc of plywood would work just as well). This distributes the force and should let the cover last longer.
I initially threaded the aluminum stock but found that the threads wore out so I eventually made a recess and epoxied a bolt into it - this seems to work well.
Ok, so back to the Lager.
The brew is transferred to the keg-fermenter, the lid is applied, bung is in place etc.
Then a "brew belt" or similar low wattage heater is applied to the outside of the fermenter and tied into your temperature controlled (In my case, a typical STC-1000 that I fit into an outdoor electrical box - this one is only wired for Heat/No-Heat cycles) and connect the temperature probe to the outside of the fermenter ( taped on with a cozy piece of rigid foam - don't worry about having the probe "in" the beer, 10G of beer has enough thermal inertia vs. the low wattage heater that a little bit of measurement latency is not an issue).
Then, insulate your fermenter. The colder your weather, the more insulation you might need. I my case, since the lowest low will be about 10C below my target (and then only for a brief time), a single old sleeping bag will do the trick.
The only other bit to mention is, that if you are not used to doing batches larger than 5G, please remember that this will be very heavy and you probably don't want to try lifting it yourself. My fermenter sits up on a platform of two old car tires with an old wooden chopping block as a table top. From this height I can syphon directly into my Corny kegs.
One more note, This batch of Lager was done using high gravity brewing. I do up a batch of double strength wort then add an equal part of clean water. Perhaps another day I will discuss this technique.
Some handy links:
STC-1000 (cheaper on Ebay)
Some handy links:
STC-1000 (cheaper on Ebay)
Lots about how to Machine Lucite/Acrylic